1. Field of the Invention
This invention relates generally to the field drywall construction and more particularly to a system of exterior and interior drywall seams and corners that greatly reduces the amount of time, labor and material required to finish a modern structure. In particular a break-apart drywall corner piece.
2. Description of Related Art
The use of gypsum drywall board in modern construction is well known. Manufactured drywall sheets are nailed to studs to form interior walls and ceilings. Before these sheets can be painted or textured, the joints must be taped and sealed with joint sealing compound (drywall mud). Drywall tape is a porous fibrous material, usually paper, which is designed to permanently bond with drywall mud.
Taping also (known as stringing) is a tedious process. First, mud and tape must be applied by hand or dispensed with a tool known as a bazooka. The worker rolls and glazes the tape while the mud is wet. As the tape strings out, it has a tendency to pull in the direction of motion. After the tape is applied, it is coated with additional mud and the edges are feathered with a wide blade drywall knife to form a smooth transition between the seam and the wall. The mud is then allowed to dry, typically overnight. Next, the seam is sanded, recoated with mud, dried and sanded again. The process is repeated if necessary until a smooth seam is produced.
Corners present a special problem. Inside corners are finished using drywall tape in much the same manner as flat joints. Outside corners are typically finished with corner beads.
Corner beads are either sharp edged or rounded nose, also known as xe2x80x9cbullnose.xe2x80x9d These are used on exterior corners at windows and other openings. To use a standard corner bead, it first must be cut from a standard length of 8 feet or 10 feet.
The bead is nailed into position using short nails approximately every foot. The worker must: 1) keep the bead plumb or level, and 2) keep the bead at the proper angle to prevent slipping too far to one side or the other. If this latter condition occurs, a xe2x80x9cshinerxe2x80x9d, as it is called in the trade, results. This is where the bead is too far toward one side of the corner making the other side flange hard to coat.
Once the bead is installed, the worker must xe2x80x9cfirst coatxe2x80x9d the bead. This means to coat it with mud for the first time. This is very labor intensive, and it uses a large amount of mud. The bead projects outwardly from the corner. Accordingly, when first coat is applied a wedge of mud is formed which is thickest at the bead and tapers out to meet the wall. After the first coat, the mud is allowed to dry. Drying takes about a day.
After the xe2x80x9cfirst coatxe2x80x9d is dry throughout the building, the worker has to sand this first coat of mud and clean all the metal edges. This is especially difficult with bullnose bead. After the xe2x80x9cfirst coatxe2x80x9d is sanded, the worker proceeds to xe2x80x9csecond coatxe2x80x9d the bead repeating the entire process again and waiting another day to dry. The worker finally must again sand the bead carefully looking for imperfections, and touching these up. At this point, the bead is ready for texture or paint. The entire process uses considerable mud, and is very labor intensive, especially the sanding. In terms of total construction time, it requires two to three days to complete all the corners of a typical residence.
An alternative to fixed corner beads, especially for corners that do not meet at 90 degrees is a product known as xe2x80x9cflex bead.xe2x80x9d Flex bead consists of two thin strips of metal bonded to a two inch paper tape. To use xe2x80x9cflex beadxe2x80x9d, a worker first spreads all-purpose mud along the wallboard on both sides of the angle. A length of xe2x80x9cflex beadxe2x80x9d is folded by hand to create a crease. The bead is then installed in the angle. This requires a good eye for straight lines since the xe2x80x9cflex beadxe2x80x9d will not make a straight line by itself. The worker must move the bead around to the best of his abilities to set it as straight as possible. On many occasions, the worker will end up with a line that is not straight; this condition is called xe2x80x9csnakingxe2x80x9d.
Once the xe2x80x9cflex beadxe2x80x9d is installed and dry, the first coat procedure is started. Most journeymen only coat one side of the angle at a time. If one tries to coat both sides at the same time, the mud flops over to the other side, and the knife digs a line into the mud on the other side of the angle. Therefore, the following process is usually used: 1) Apply a first coat of mud to one side and wait until it is dry; 2) Apply a first coat of mud to the other side and wait until it is dry; 3) Sand both sides and clean at the crease; 4) Apply a second coat of mud to one side and wait until it is dry; 5) Apply a second coat of mud to the other side and wait until it is dry; 6) Sand and touch up both sides. This process is tedious, and requires considerable time while the respective sides are drying. Accordingly, considerable drawbacks remain unsatisfied.
What is badly needed is a system for finishing drywall on the interior of buildings that avoids the difficulties of taping, corner beads and xe2x80x9cflex beadxe2x80x9d while retaining the perfect finished appearance that is required for texturing or painting. The sanding steps should be reduced or eliminated. This system should reduce the labor to less than one day for a typical residence and significantly reduce the amount of mud used.
The present invention relates to a drywall finishing system for finishing 1) inside and outside corners of any angle, 2) stub, end or closet walls, 3) window wrap corners, and 4) L-member for window sills and areas where a drywall ends against another surface e.g. brick. In addition, the system includes accessory products for each of the pieces mentioned. In particular the invention includes a break-apart bead.
The drywall finishing system of the invention in its most basic form is an elongated, preformed trim piece comprising a semi-rigid member having two flanges and inner and outer surfaces. The inner surface is provided with bonding means for continuously bonding the semi-rigid member to the drywall. The outer surface of the finishing member is provided with finishing means adapted to receive paint or other texture. The flanges of the semi-rigid member are tapered in a lateral direction, being thickest at the center and tapering to a thin edge.
A first preferred embodiment is a flexible trim piece, comprising a semi-ridged member having two flanges, each of the flanges being tapered to a thin lateral edge. The semi-rigid member has a longitudinal groove between the flanges forming a hinge. A covering material is bonded to the inside surface of the semi-rigid member. The covering material is preferably drywall tape for forming a good continuous bond with drywall mud between the trim piece and the drywall. A finishing material is bonded to the exterior surface of the semi-rigid member. The finishing material is preferably a fibrous material such as a paper which is suitable for directly receiving paint or other texture. The finishing material may desirably extend laterally beyond the respective side edges of the semi-rigid member forming side tabs.
To install the first embodiment of the invention, a length of preformed trim piece is selected from stock and cut to length if not exactly the right length. A flat coat of mud is applied to both sides of a drywall corner. The preformed piece is folded at the groove to match the corner, and placed over the mud and smoothed into place. Since the trim piece of the invention is preformed, the piece makes a straight line at the required angle. Once, the piece is in place, the edges are feathered or xe2x80x9ckilledxe2x80x9d once with a small amount of mud and a wide drywall blade or knife. At that point the corner is complete except for drying. It requires little or no sanding. After the mud has dried, the finishing material can be directly textured or painted.
The present invention is placed on top of a coat of applied mud at the corner. The corner can be an exterior or interior angle. No nails are required, since the invention pieces stick to the mud. The exterior finishing material is paper, plastic, or other suitable material for receiving texture or paint. The present invention eliminates most of the intense labor associated with present methods since none of the parts need to be coated with mud or sanded. In addition, the parts form straight, finished lines and angles as soon as they are installed.
Additional embodiments of the invention include right angle outside corner trim pieces, bullnose outside corner trim pieces, stub or end wall trim pieces, U-shaped and V-shaped joint pieces, and other trim and specialty pieces including a break-apart bead.
One embodiment of the present invention relates to a break-apart bead, a rigid corner bead that can be used as a rigid bead most of the time. The most common angle is 90 degrees, so the preferred method of making the present invention is around 89 degrees to fit a 90 degree corner; however, this is not necessary to the functioning or principle of the invention and any rigid angle can be used.
As long as the installer encounters corners of the angle that the present invention is supplied in, the corner seams are installed and finished in a normal way. However, when an angle that is different that the stock piece is encountered, the present invention is snapped apart and now fits the new angle. This is accomplished by extruding a piece of flex-trim as described in U.S. Pat. No. 6,148,573. This flex-trim comprises a semi-rigid center section bonded to outer layers of paper or other fibrous material. The inside, or drywall surface, is usually made of standard drywall paper. The outside surface is prepared to receive paint or texture and can be made from cup-stock paper (like is used to manufacture paper cups). The interior semi-rigid layer is usually hi-impact polystyrene or other high impact plastic or other material. This material is usually tapered so that it is thicker in the middle and thinner at the edges. A groove or score runs longitudinally down the center of the piece forming a hinge so that, as extruded, the piece can match any angle.
The embodiment being described takes this flex-trim piece and glues, bonds, or extrudes it to a fixed rigid angle (usually around 89 degrees) after or during extrusion. This is done either by running the piece past a glue gun nozzle to lay a bead of glue along the hinge to hold it to a predetermined angle, or by causing a small connecting ridge to be formed during extrusion. The piece can also be fixed folded to the desired angle and a glue gun can be run along the piece.
The glue quickly dries forming a rigid piece formed to a fixed angle, or in the case of extrusion the piece is extruded at a fixed angle. As previously stated, as long as the installer encounters standard angles, the piece is used as a rigid piece at the fixed angle; however, when the installer encounters a non-standard angle, all that is necessary is that the installer pop or snap the piece apart breaking the small bead along the length. Now the piece again becomes a true flex-trim allowing installation at any angle.
The piece has the convenience of a rigid, fixed corner as long as that type of corner is needed and a flexible trim piece when some other angle is needed. The piece can be installed as described in U.S. Pat. No. 6,148,573 by first putting mud on both sides of a corner, pressing the piece into position, and then killing the edges with a small amount of finishing mud and a wide blade knife. The piece is then finished without further work.
When the mud is dry, the piece can directly receive paint or texture without sanding.
It should be noted that this type of piece can be made for strictly exterior trims, strictly interior trims, or for a trim that can be used on exterior and interior corners. When the piece is made for strictly exterior corners, it is usually heavier and thicker than when it is made for strictly interior corners. When the present invention is used on a trim that can be applied to either exterior or interior corners, it can be made of an intermediate thickness and weight to fit the job.
These advantages and other advantages of the present invention will become more fully apparent from the following detailed description when read in conjunction with the accompanying drawings.